DE102015214362A1 - Microelectromechanical device - Google Patents

Abstract

The invention relates to a microelectromechanical device comprising: a magnet (102, 202) arranged on a substrate top side (101a) of a substrate (101) and / or on a substrate rear side (101b) of the substrate (101); a microwave transmitter (503) integrated in the substrate (101); a microwave receiver (506) integrated in the substrate (101); and an absorber level (203) spaced from the substrate with a paramagnetic layer (201) facing the substrate (101) and an infrared absorber layer (107) facing away from the substrate (101).

Description

The present invention relates to a microelectromechanical device, a manufacturing method for a microelectromechanical device, a use of a microelectromechanical device as a bolometer, and a measuring device for measuring a temperature distribution.

State of the art

Microelectromechanical bolometers can measure electromagnetic radiation intensities in a specific wavelength range (about 3 to 15 microns). The bolometer comprises an absorber, which converts the electromagnetic radiation into heat. The temperature increase of the absorber is measured and deduced on the intensity of the electromagnetic radiation and the object temperature.

For example, is from the DE 11 2006 004 013 B4 a bolometer is known in which the heating of the absorber is measured by means of an electrical resistance.

Disclosure of the invention

According to a first aspect, the present invention provides a microelectromechanical device having a magnet arranged on a substrate top side and / or a substrate back side of the substrate, a microwave transmitter integrated in the substrate, a microwave receiver integrated in the substrate and an absorber level spaced from the substrate. The absorber level comprises a paramagnetic layer facing the substrate and an infrared absorber layer facing away from the substrate. The term "level" here refers to a platform which is arranged above a substrate and spaced therefrom.

The present invention according to a second aspect provides a manufacturing method for a microelectromechanical device. For this purpose, a substrate is provided with a microwave transmitter integrated in the substrate and a microwave receiver integrated in the substrate. Subsequently, an electromagnet is formed on a substrate top side of the substrate and / or a magnet is formed on a substrate back side of the substrate. A sacrificial layer is applied to the substrate top. A paramagnetic layer is deposited on the sacrificial layer and patterned. An absorber layer is applied to the paramagnetic layer and patterned leaving at least one support arm exposed. Subsequently, the sacrificial layer is removed.

The present invention according to a third aspect provides a use of a microelectromechanical device as a bolometer. For this purpose, microwave radiation is emitted by the microwave transmitter and the microwave radiation reflected by the absorber level is received by the microwave receiver. An absorption spectrum of the absorber level is determined from the received microwave radiation and a temperature of the absorber level is determined from an absorption width of the calculated absorption spectrum.

The present invention according to a fourth aspect provides a measuring device for measuring a temperature distribution having a plurality of bolometers arranged in an array on a common substrate. In this case, the microelectromechanical bolometers in each row of the array have a common microwave transmitter integrated in the substrate. Furthermore, the bolometers in each column of the array have a common microwave receiver integrated in the substrate.

Preferred developments are the subject of the respective subclaims.

Advantages of the invention

In contrast to a bolometer, in which the heating of the absorber is measured by means of a resistor, in the microelectromechanical device according to the invention an electrical contacting of the absorber level is not necessary. As a result, only a few process steps are necessary because the contacting of the absorber level and the formation of the resistance omitted. The same advantage also applies to other thermoelectric conversion elements, e.g. Diodes. By using a device according to the invention also eliminates a current flow with a corresponding loss of power conversion within the thermoelectric conversion element, which leads to a heating of the bolometer, which must be compensated, for example, additional reference pixels with appropriate space requirements.

Since no electrical connection between absorber level and substrate is necessary, the thermal coupling of absorber level and substrate is minimized. This leads to a stronger heating of the absorber and a larger measurement signal.

Due to the low thermal mass of the absorber level, a very rapid determination of the temperature of the absorber level is possible. The determination of the temperature of the absorber level can thereby be fast and with a high Accuracy be performed. As a result, high frame rates (frame rates) are possible when used in imaging systems.

In another aspect, the present invention provides a microelectromechanical device wherein the paramagnetic layer comprises manganates, particularly La _0.62 Bi _0.05 Ca _0.33 MnO ₃ , and / or La _0.67 Sr _0.33 MnO ₃ . For the mentioned manganates, the relationship between the width of the absorption spectrum and the temperature of the absorber level is well studied. Therefore, by determining the absorption spectrum, the temperature of the absorber level and thereby the intensity of the incident electromagnetic radiation can be determined with great precision. As explained below, the absorption width of the absorption spectrum increases linearly with temperature. As a result, the temperature can be measured more accurately and with less electronics and computing power than would be the case, for example, in a non-linear relationship.

In another aspect, the present invention provides a microelectromechanical device wherein the infrared absorber layer comprises silicon oxide.

According to a further aspect, the present invention provides a microelectromechanical device, wherein metal elements are integrated into the infrared absorber layer as plasmonic absorbers, in particular metal mirrors, metallic disks, metallic crosses, metallic lattices and / or metal antenna structures. By using metal elements integrated in the infrared absorbing layer, the infrared absorbing ability of the infrared absorbing layer can be increased. This ensures efficient and uniform heating of the absorber level.

In another aspect, the present invention provides a microelectromechanical device wherein a layer thickness of the absorber layer is less than or equal to 1.6 microns.

In another aspect, the present invention provides a microelectromechanical device using gunnodes and / or waveguides as microwave transmitters.

According to a further aspect, the present invention provides a microelectromechanical device, wherein an electromagnet is arranged on the substrate upper side and a permanent magnet on the substrate back side. By using an electromagnet, the strength of the applied magnetic field can be controlled. Increasing the applied magnetic field increases the measurement accuracy of the bolometer used.

Advantages of the invention

Brief description of the drawings

Show it:

1 a schematic oblique view of an embodiment of a micro-electro-mechanical device;

2 a schematic cross-sectional view of the microelectromechanical device according to the embodiment;

3 a flowchart for explaining an embodiment of a manufacturing method of a micro-electro-mechanical device;

4 to 8th schematic cross-sectional views for explaining the embodiment of the manufacturing method of the microelectromechanical device;

9 a flowchart for explaining a use according to the invention of the microelectromechanical device as a bolometer;

10 a schematic absorption spectrum;

11 a diagram for explaining the relationship of temperature and absorption width; and

12 a schematic plan view of an apparatus for measuring a temperature distribution.

In all figures, the same or functionally identical elements and devices - unless otherwise stated - provided with the same reference numerals.

Description of the embodiments

1 shows a schematic oblique view of an embodiment of a microelectromechanical device 100 according to the present invention and 2 shows a schematic cross-sectional view of the microelectromechanical device 100 along the axis II. On a substrate back 101b a substrate 101 , which may be made of a silicon wafer, for example, is a permanent magnet layer 202 educated. On a substrate top 101 of the substrate 101 is a coil 102 arranged, which preferably consists of copper. The sink 102 serves as an electromagnet, whereby by applying a electric current is induced a magnetic field. The total magnetic field strength of the permanent magnet layer 202 and the coil 102 generated magnetic field is chosen as large as possible, preferably 1 to 2 Tesla.

The invention is not limited thereto. For example, only one permanent magnet layer 202 on the substrate back 101b be upset and the coil 102 missing or it can only be a coil 102 on the substrate top 101 be arranged, the permanent magnet layer 202 but missing.

In an absorber level distance d ₅ is an absorber level 203 , The absorber level distance d ₅ is in this case selected to be approximately equal to one fourth of the wavelength λ to be detected, that is d ₅ = λ: 4. Preferably, the absorber level distance d ₅ is in the range of 1 to 5 micrometers, especially ₅ d = 2.5 micrometers. The absorber level 203 has a paramagnetic layer 201 which is the substrate 101 facing and a substrate remote from the infrared absorber layer 107 on. The material of the paramagnetic layer 201 preferably comprises manganates, in particular La _0.62 Bi _0.05 Ca _0.33 MnO ₃ and / or La _0.67 Sr _0.33 MnO ₃ . The layer thickness d _{4 of} the paramagnetic layer 201 is between 50 and 800 nanometers, preferably the layer thickness d _{4 of} the paramagnetic layer 201 equal to 300 nanometers. The infrared absorber layer 107 has a layer thickness d ₃ of less than 3 microns, preferably less than or equal to 1.6 microns.

Preferably, in the infrared absorber layer 107 Metal elements integrated as plasmonic absorber. The metal elements may in particular comprise metal mirrors, metallic disks, metallic crosses, metallic grids and / or metal antenna structures.

The absorber level 203 is through a first sleeve 104 , which has a first pillar 106 connected to the substrate and a second retaining sleeve 103 , which has a second column 105 with the substrate 101 is fixed, hovering above the substrate. The first sleeve 104 and the second tether 103 consist here preferably of silicon oxide and each have a width d ₁ of 100 nanometers to 1000 nanometers, preferably equal to 500 nanometers and one perpendicular to the substrate 101 measured thickness d ₂ from about 100 nanometers to 1000 nanometers, preferably equal to 400 nanometers.

However, the invention is not limited thereto. So can the sleeves 103 . 104 also on a (not shown) layer which ends on the substrate 101 around the microelectromechanical device 100 is formed around and up to the height of the tufts 103 . 104 up enough.

In the substrate 101 is a microwave transmitter 503 integrated, which consists of a waveguide, wherein the waveguide a first microwave transmitter section 501 and a second microwave transmitter section 502 includes, which along the dashed axes 501 respectively. 502a below the absorber level 203 run.

Furthermore, in the substrate 101 a microwave receiver 506 integrated, which consists of a waveguide, wherein the waveguide a first microwave receiver section 504 and a second microwave receiver section 505 includes, which along the dashed lines 504a respectively. 505a run below the absorber level. The microwave transmitter sections 501 . 502 and the microwave receiver sections 504 . 505 are essentially perpendicular to each other here.

The invention is not limited thereto. Thus Gunndioden instead of waveguides can be used as a microwave transmitter and / or receiver.

3 shows a flowchart for explaining an embodiment of a manufacturing method of a microelectromechanical device 100 according to the present invention.

As in 4 is shown, in a first step S1, a substrate 101 , which is preferably made of a silicon wafer, provided. In the substrate 101 are a microwave transmitter 503 and a microwave receiver 506 integrated, which is a first microwave transmitter section 501 and a second microwave transmitter section 502 or a first microwave receiver section 504 and a second microwave receiver section 505 include, which are substantially perpendicular to each other.

In a second step S2, a permanent magnet layer is formed 202 on a substrate back 101b of the substrate 101 formed, for example, in thin-film technology. On a substrate top 101 of the substrate 101 becomes a coil 102 arranged, which is connected to a control unit, not shown, and is designed to generate a magnetic field.

As in 5 is shown, in a third step S3, a sacrificial layer 601 on the substrate surface 101 of the substrate 101 applied. The layer thickness of the sacrificial layer corresponds to the later absorber level distance d ₅ and is between 1 and 5 microns and is preferably equal to 2.5 microns.

In a fourth step S4 becomes a paramagnetic layer 201 applied on the sacrificial layer. The layer thickness d _{4 of} the paramagnetic layer 201 is between 50 nanometers and 800 nanometers and is preferably equal to 300 nanometers. The paramagnetic layer 201 is patterned, for example, by etching or by means of a laser such that a cuboid with a square surface is formed, which has a dimension of between about 5 microns × 5 microns to 100 microns × 100 microns. The paramagnetic layer 201 preferably comprises manganates, in particular La _0.62 Bi _0.05 Ca _0.33 MnO ₃ , and / or La _0.67 Sr _0.33 MnO ₃ .

In a fifth step S5 becomes an absorber layer 107 on the paramagnetic layer 201 educated. For this, first, as in 6 shown a first oxide layer 604 , preferably of silicon oxide, on the sacrificial layer 601 and the paramagnetic layer 201 educated. The thickness d _{2 of} the first oxide layer 604 is greater than the layer thickness d _{4 of} the paramagnetic layer 201 and is for example between 100 and 1000 nanometers and is preferably 400 nanometers. On the first oxide layer 604 become a first metal structure 602 and a second metal structure 603 having a width d ₁ between 100 to 1000 nanometers, preferably equal to 500 nanometers, deposited. These metal structures are etch-resistant and correspond in shape to a later to be formed first retaining sleeve 104 and second tucks 103 ,

On the first oxide layer 604 will be an in 7 shown second oxide layer 701 applied. A layer thickness d _{6 of} the second oxide layer 701 plus the thickness d _{2 of} the first oxide layer 604 corresponds to the layer thickness d _{4 of} the paramagnetic layer 201 plus a layer thickness d _{3 of} an infrared absorber layer 107 as well as in 2 illustrated.

This infrared absorber layer 107 is by etching the second oxide layer 701 and the first oxide layer 604 , as in 8th shown, exempted. In addition, the etch process becomes a first retainer 104 and a second tuck 103 whose shape is due to the first metal structure 602 or by the second metal structure 603 is fixed, structured. Subsequently, the first metal structure 602 and the second metal structure 603 away.

Finally, in a sixth step, S6 is made by trench etching the sacrificial layer 601 an absorber level 203 which is the paramagnetic layer 201 and the infrared absorber layer 107 comprises, exempted, whereby an in 1 shown micromechanical structure 100 is formed.

The invention is not limited to said embodiment. For example, forming the permanent magnet layer 202 on the substrate base 101b be performed only at the end of the manufacturing process. Furthermore, only one permanent magnet layer can also be used 202 or a coil 102 be formed. In addition, the microelectromechanical device 100 vacuum-capped by a low-temperature bonding process.

9 shows a flowchart for explaining a use of the microelectromechanical device according to the invention 100 as a bolometer. In a first step S10, the microwave transmitter transmits 503 Microwave radiation, which from the paramagnetic layer 201 is absorbed.

In a second step S20, the microwave radiation, which has been reflected by the absorber level, from the microwave receiver 506 received and determined in a third step S30, the absorption spectrum based on the received microwave radiation, for example by an evaluation unit, not shown. The determination of the absorption spectrum can be carried out by reflection or transmission methods. Here, the microwave signal from the microwave transmitter 503 such that the magnetic field component of the microwave signal is substantially perpendicular to the field lines of the coil 102 and permanent magnet layer 202 generated magnetic field is.

10 shows a typical absorption spectrum 1000 for a transmitted microwave radiation with a frequency of 9388.2 MHz for a fixed temperature of the paramagnetic layer 201 , The signal strength S of the microwave spectrum 1000 is measured as a function of the magnetic field strength G, that of the coil 102 and the permanent magnet layer 202 is generated, applied. The absorption spectrum 1000 has an absorption width. As in 11 shown, the absorption width has a largely linear dependence on the temperature of the paramagnetic layer 201 on. The exact form of dependence depends on the material used for the paramagnetic layer 201 from. In 11 Two different materials are recorded, namely La _0.67 Sr _0.33 MnO ₃ and La _0.62 Bi _0.05 Ca _0.33 MnO ₃ .

In the 11 The picture shown is from the following publication: Seehra, MS, et al., "The linear temperature dependence of the paramagnetic resonance linewidth in the manganate perovskites La0.67 Sr0.33 MnO3 and La0.62 Bi0.05 Ca0.33 MnO3, "Journal of Physics: Condensed Matter Vol. 50 (1996), page 11283 ,

Based on the absorption spectrum, the absorption width can be determined. Based on the 11 known linear relationship between absorption width and temperature T can in known material of the paramagnetic layer 201 the temperature T of the paramagnetic layer 201 and thus the absorber level 203 be determined in a fourth step S40. From the temperature T of the absorber level can be deduced the intensity of the irradiated electromagnetic radiation.

12 shows a measuring device 300 for measuring a temperature distribution. The measuring device 300 comprises a plurality of bolometers according to the invention A ₁ to A ₆ , B ₁ to B ₆ and C ₁ to C ₆ . The bolometers can be one of the embodiments described above. The bolometers are arranged in the illustrated embodiment in an array with three rows and six columns. The number of bolometers is not limited to this and in particular can be significantly higher. Below the six bolometers A ₁ to A _{6 of} the top row, a first microwave transmitter extends in the substrate 301 which is formed as described above as a waveguide for emitting microwave radiation for the respective bolometer. Parallel to this, a second microwave transmitter runs under the six bolometers B ₁ to B _{6 of} the second row in the substrate 302 and among the six bolometers C ₁ to C ₆ in the substrate a third microwave transmitter 303 , Perpendicular to the microwave transmitters 301 to 303 In each case, a first to sixth microwave receiver run under the bolometers of the first to sixth column of the array 311 to 316 ,

The microwave transmitter 301 to 303 Send now successively microwave signals. First, the first microwave transmitter sends 301 a signal P _in1 , which is emitted from a left side, that is from the bolometer A ₁ to the bolometer A ₆ out. The microwave receiver 311 to 316 receive at the same time reflected from the absorber _{levels of} the bolometer microwave signal P _out1 to P _out6 . The first microwave receiver 311 hereby measures the absorption spectrum of the bolometer A ₁ , the second microwave receiver 312 measures the absorption spectrum of the bolometer A ₁ and the bolometer A ₂ , etc., while the sixth microwave receiver 316 measures the total absorption spectrum of bolometers A ₁ through A ₆ inclusive. By subtracting measured absorption spectra, the absorption spectrum of the respective bolometer can be measured. For example, the absorption spectrum of the fifth bolometer A ₅ by subtracting the fourth means of the microwave receiver 314 received absorption spectrum of the means of the fifth microwave receiver 315 measured absorption spectrum can be measured. From the absorption spectrum thus calculated, the temperature of the corresponding bolometer can be calculated.

Similarly, the temperatures of the second and third row bolometers of the array can be measured, with the second microwave transmitter 302 or third microwave transmitter 303 a signal P or a signal _in2 P _in3 emits.

On the basis of the measured temperatures of the individual bolometers a temperature distribution can be measured.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 112006004013 B4 [0003]

Cited non-patent literature

• Seehra, MS, et al., Journal of Physics: Condensed Matter Vol. 8, no. 50 (1996), page 11283 [0050]

Claims (10)

Microelectromechanical device ( 100 ) with: one on a substrate top side ( 101 ) of a substrate ( 101 ) and / or one on a substrate back ( 101b ) of the substrate ( 101 ) arranged magnets ( 102 . 202 ); one in the substrate ( 101 ) integrated microwave transmitter ( 503 ); one in the substrate ( 101 ) integrated microwave receiver ( 506 ); and an absorber level spaced from the substrate (US Pat. 203 ) with a substrate ( 101 ) facing paramagnetic layer ( 201 ) and one from the substrate ( 101 ) remote infrared absorber layer ( 107 ). Microelectromechanical device ( 100 ) according to claim 1, wherein the paramagnetic layer ( 201 ) Manganates, in particular La _0.62 Bi _0.05 Ca _0.33 MnO ₃ and / or La _0.67 Sr _0.33 MnO ₃ comprises. Microelectromechanical device ( 100 ) according to one of claims 1 or 2, wherein the infrared absorber layer ( 107 ) Comprises silica. Microelectromechanical device ( 100 ) according to one of the preceding claims, wherein in the infrared absorber layer ( 107 ) Metal elements as plasmonic absorber, in particular metal mirror, metallic discs, metallic crosses, metallic lattices and / or antenna structures of metal are integrated. Microelectromechanical device ( 100 ) according to one of the preceding claims, wherein a layer thickness of the absorber layer ( 107 ) is less than or equal to 1.6 microns. Microelectromechanical device ( 100 ) according to one of the preceding claims, wherein as microwave transmitter ( 503 ) Gunn diodes and / or waveguides are used. Microelectromechanical device ( 100 ) according to one of the preceding claims, wherein at the substrate top ( 101 ) an electromagnet ( 102 ) and at the back of the substrate ( 101b ) a permanent magnet ( 202 ) is arranged. Manufacturing Method for a Microelectromechanical Device ( 100 comprising the steps of: providing (S1) a substrate ( 101 ) with one in the substrate ( 101 ) integrated microwave transmitter ( 503 ) and one in the substrate ( 101 ) integrated microwave receiver ( 506 ); Forming (S2) an electromagnet ( 102 ) on a substrate top side ( 101 ) of the substrate ( 101 ) and / or forming a magnet ( 202 ) on a substrate back side ( 101b ) of the substrate ( 101 ); Applying (S3) a sacrificial layer ( 601 ) on the substrate top ( 101 ); Application and structuring (S4) of a paramagnetic layer ( 201 ) on the sacrificial layer ( 601 ); Application and structuring (S5) of an absorber layer ( 107 ) on the paramagnetic layer ( 201 ), wherein at least one holding arm is released; and removing (S6) the sacrificial layer ( 601 ). Use of a microelectromechanical device ( 100 ) according to one of claims 1 to 7 as a bolometer, comprising the steps of: emitting (S10) microwave radiation through the microwave transmitter ( 503 ); Receive (S20) that of the absorber level (S20) 203 ) reflected microwave radiation through the microwave receiver ( 506 ); Determining (S30) an absorption spectrum of the absorber level ( 203 ) based on the received microwave radiation; Determining (S40) a temperature of the absorber level (S40) 203 ) on the basis of an absorption width (σ) of the calculated absorption spectrum. Measuring device ( 300 ) for measuring a temperature distribution with a plurality of in an array on a common substrate ( 101 ) arranged bolometers (A ₁ to A ₆ , B ₁ to B ₆ , C ₁ to C ₆ ) according to claim 9; wherein the microelectromechanical bolometers in each row of the array have a common in the substrate ( 101 ) integrated microwave transmitter ( 301 to 303 ) exhibit; and wherein the bolometers in each column of the array share a common one in the substrate ( 101 ) integrated microwave receiver ( 311 to 316 ) exhibit.

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